Synergistic Passivation Strategy for Efficient and Stable Perovskite Solar Cells

ABSTRACT Passivating surface defects is crucial for the performance of inverted perovskite solar cells (PSCs). Single molecules struggle to passivate multiple perovskite surface defects, significantly limiting the performance of perovskite solar cells. Here, we report a bimolecular synergistic passivation strategy combining propane‐1,3‐diamine dihydroiodate (PDADI) and 11‐mercaptoundecanoic acid (MUA) to achieve a complementary passivation effect. PDADI provides efficient field‐effect passivation and halide vacancy filling, while MUA further chemically passivates defects through its strong coordinating groups (‐SH/‐COOH). This synergistic effect reduces the trap‐state density from 3.00 × 10 15 to 1.65 × 10 15 cm −3 , and also modulates the perovskite energy level. The champion device with the synergistic passivation achieves an efficiency of 26.15 % with long‐term stability (maintained the initial efficiency of 90 % after 1000 and 200 h under ISOS‐D‐1 and ISOS‐L‐3). This work provides an effective approach for designing high‐performance, highly stable perovskite solar cells through synergistic passivation.